The Mars Science Laboratory, the "nuclear-powered robot laser tank" carrying NASA's shiny new rover, Curiosity, is due to fire its engine in two days' time for the biggest manoeuvre on its trip to the Red Planet.

Artist's concept of MSL during cruise phase. Credit: NASA/JPL-Caltech

On Wednesday night at 11pm GMT, the MSL will fire its eight thruster engines in a choreographed sequence over almost three hours to direct itself more precisely at the Gale Crater on Mars.

When the MSL took off in late November, its trajectory was deliberately aimed at missing the Red Planet to make sure the upper stage of the launch vehicle wouldn't land there when it's discarded by the ship. The laboratory itself was cleaned to protect Mars from Earth's microbes, but the upper stage was not.

As well as shunting the craft onto the right course, the engine dance will also increase the velocity by about 12.3 miles an hour (about 20kmph).

"After this trajectory correction manoeuvre, we expect to be very close to where we ultimately need to be for our entry point at the top of the Martian atmosphere," said MSL cruise mission manager Arthur Amador, in a canned statement.

The MSL is due to arrive at the planet on 6 August, which gives the spacelab five more chances to correct its flight path, if it needs them.

The upcoming manoeuvre will use the MSL's inertial measurement unit to figure out the craft's orientation and acceleration while the engines burn. The unit is being used as an alternative to the onboard celestial navigation system, which was accidentally reset on 29 November when the MSL used its star-identifying software.

On Sunday, the MSL's operations team will start a set of engineering checks, lasting around a week, which will test several parts of the system for landing Curiosity on Mars and for the rover's communication with Mars orbiters. ®